1. Field of the Invention
The present invention relates to devices for comminuting solid materials through a rapid reduction in pressure surrounding the materials, and more particularly, to a device using a rotating blade to effect the pressure reduction.
2. Description of the Prior Art
A device for comminuting solid particles is disclosed in U.S. Pat. No. 3,255,793 to Clute. The device disclosed in that patent provides a rotatable fan having blades 80 tangentially extending from a hub 70 which is attached to a front end of a cantilevered shaft 48. A housing just preceeding the fan is constructed to be enlarged directly adjacent to the fan to cause a reduction of pressure in the housing adjacent the fan to effect the explosive comminution of the particles.
The fan shaft 48 is carried in bearings 42 and 44, both of which are outside of the housing and spaced behind the fan. The fan blades are formed as a cast assembly and are shaped in a concave lateral cross-section to act as elongated cups to push air through the housing. Thus, the windage effect on the fan blades is quite high.
A comminution device is also disclosed in U.S. Pat. No. 4,390,131 to Pickrel which, does not use a rotating fan, but rather uses a plurality of tangentially introduced air flows. However, the text of the patent does discuss the patent to Clute and states that the vanes of the blower rotor, being subject to comminuted material, wear rapidly, particularly at the tips and the leading edges, causing great expense in replacement of the blades. Also, the wear of the blades tends to be uneven so that undue vibration often requires the rotor to be replaced before any vanes are worn out.
The patent to Pickrel also discusses the use of a comminutor having a fan with inclined blades rather than the trough-like section of Clute, but otherwise corresponding thereto, of a particular size and dimension which was fed with gold ore at the rate of one ton per hour and the fan required replacement at the end of one hundred hours of operation. It was also suggested that since the fan shaft was over hanging (cantilevered), the bearings for the shaft also became unduly worn.
Another patent disclosing a comminution device is No. 4,391,411 to Colburn who again discusses the patent to Clute and suggests a means of improving on that concept by attaching essentially two substantially similar comminution devices in a serial arrangement to effect two comminution events, one after the other, and requiring only a single dust collecting apparatus. Colburn also suggests that the first inlet should be vertical so that the material may be admitted in a gravity assisted manner to reduce the energy required to accelerate the particles toward the first rotating fan.